Light emitting diode structures

• US 20060062540A1
• Filed: 09/22/2004
• Published: 03/23/2006
• Est. Priority Date: 09/22/2004
• Status: Active Grant

• Current Assignee: Quantum NIL Limited, Quantum NIL Limited Taiwan Branch
• Original Assignee: Mesophotonics Limited
• Inventors: Zoorob, Majd, Lincoln, John
• Granted Patent: US 7,509,012 B2
• Time in Patent Office: Days
• US Class Current: 385/147
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01L 2933/0083 Periodic patterns for optical field-shaping in or on the semiconductor body or semiconductor body package, e.g. photonic bandgap structures
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/24 of the light emitting region, e.g. non-planar junction

Abstract

According to one aspect of the present invention, a light emitting diode (LED) structure including an active core layer and at least one substrate layer having a first refractive index, comprises a 2-dimensional photonic quasicrystal in the structure, the photonic quasicrystal comprising an array of regions having a second refractive index, the array exhibiting long range order but short range disorder. The long range order is associated with diffractive properties of the structure and gives rise to uniform-far field diffraction patterns from the LED. The present invention enjoys the benefit of improved light extraction from LEDs without undesirable far field illumination patterns.

Claims

1. A light emitting diode (LED) structure including an active core layer and at least one substrate layer having a first refractive index, comprising a 2-dimensional photonic quasicrystal in the substrate layer, the photonic quasicrystal comprising an array of regions having a second refractive index, the array exhibiting long range order but short range disorder.

2. A light emitting diode (LED) structure according to claim 1, wherein the Fourier transform of the array has a degree of rotational symmetry n, where n>

6.

3. A light emitting diode (LED) structure according to claim 1, wherein the photonic quasicrystal is designed to have a bandgap that overlaps with the emission spectrum of the active layer in the LED.

4. A light emitting diode (LED) structure according to claim 3, wherein the bandgap extends in all directions and for all polarisations.

5. A light emitting diode (LED) structure according to claim 1, wherein the substrate layer is a dielectric layer and the quasicrystal is a variation in refractive index that extends partially or completely across the layer.

6. A light emitting diode (LED) structure according to any one of claims 1 to 4, wherein the substrate layer contains a metal layer with a quasicrystal geometry.

7. A light emitting diode (LED) structure according to claim 1, wherein the array is in the form of a Fibonacci spiral pattern.

8. A light emitting diode (LED) structure according to claim 1, wherein the array is in a Penrose tiling pattern.

9. A light emitting diode (LED) structure according to claim 1, wherein the photonic quasicrystal is in a light exiting surface layer of the light emitting diode.

10. A light emitting diode (LED) structure according to claim 1, wherein the photonic quasicrystal is between the active layer and a light exiting surface.

11. A light emitting diode (LED) structure according to claim 1, including photonic quasicrystals in more than one layer.

12. A light emitting diode (LED) structure according to claim 1, wherein the substrate layer includes a section of photonic quasicrystal that is repeated periodically.

13. A light emitting diode (LED) structure according to claim 1, wherein the photonic quasicrystal includes regions of tunable material to provide for a tunable optical output.

14. A light emitting diode (LED) structure including an active core layer and a least one substrate layer having a first refractive index, comprising a 2-dimensional photonic band structure in the substrate layer, the photonic band structure comprising an array of regions having a second refractive index, wherein each region has a predetermined constant spacing from at least one other region and each region is spaced from all other regions by a predetermined minimum distance but wherein the array of regions is amorphous.

15. A method of extracting light from an LED structure comprising the step of providing a photonic quasicrystal in a layer of the LED structure other than in an active core layer, the photonic quasicrystal exhibiting long range order but short range disorder.

16. A method of manufacturing an LED structure comprising the steps of:

providing at least one substrate layer;

providing an active core layer; and

forming a photonic quasicrystal in the substrate layer, the photonic quasicrystal exhibiting long range order but short range disorder.

17. A method of manufacturing an LED structure comprises the steps of:

providing at least one substrate layer having a first refractive index;

providing an active core layer; and

forming a photonic band structure in the substrate layer, the photonic band structure comprising an array of regions having a second refractive index, wherein each region has a predetermined constant spacing from at least one other region and each region is spaced from all other regions by a predetermined minimum distance but wherein the array of regions is amorphous.